This invention relates to a reflective device. It relates further to a method of, and means for, manufacturing the device, as well as to apparatus utilising the device.
According to the invention there is provided a reflective device which includes a plurality of reflective regions, the regions each being concave to have the same co-incident focal region and the reflective regions being disposed adjacent each other in a stepped arrangement along a reference line to have a linear extended configuration.
The device may include a plurality of sets of reflective regions having a different focal region, the device having as many focal regions as there are sets of reflective regions. In one arrangement, the reflective regions of one set may be disposed alternately with the reflective regions of another set, in a zig-zag fashion.
The reflective regions may have a linear cross-section in a plane perpendicular to the reference line, the focal region being linear and the device having a substantially planar configuration. Alternatively, all the reflective regions may have a concave cross-section in a plane perpendicular to the reference line, the focal region being a focal point.
The device may include a matrix of dished reflective regions, each reflective region being curved in two dimensions, the reflective regions being disposed along parallel reference lines lying in a plane, to form a planar device having a matrix of focal points.
Preferably, the reflective regions may be parabolic.
The device may be of silvered glass, a synthetic plastics material, or of metal. Accordingly, the device may be particularly adapted to reflect either electro-magnetic or acoustic waves.
The invention extends further to a receiver or transmitter for electro-magnetic or acoustical waves having a reflective device according to the invention.
In particular, the receiver may be an energy concentrator such as a solar heater having a reflective device according to the invention, which has focal lines, and a plurality of pipes containing a fluid to be heated arranged co-incidentally with the focal lines.
The invention still further provides a method of manufacturing a reflective device according to the invention, which includes pressing or rolling a sheet of a suitable material, such as metal, with suitable dies or rollers or includes moulding the device in a suitable mould from a glass or a synthetic plastics material, to have the required configuration.
The invention correspondingly provides a die or roller or a mould for manufacturing the reflective device. The reflective device may also be used in radio-astronomy or the like. With such an application a number of directional vanes disposed normally to the reference line may be used to allow only normal incident waves to be reflected and collected.